Problem building in a directory shared from Mac to Ubuntu

Hi,
I am observing a strange problem when I build latest PostgreSQL head on
Ubuntu 12.04. I am running Ubuntu 12.04 as VM on Mac 10.7. The build
directory points to a sub-directory of host directory shared from Mac to
Ubuntu 12.04. The source is also located in a sub-directory of the shared
directory.

postmaster builds without any error, but all the binaries in src/bin fail
to link with error "undefined reference to `pthread_sigmask'". If I add
-pthread to the link command the binaries link without error.

If I build it on a directory local to VM and also place my source in a
directory local to VM, the build goes fine.

Is this a known issue? What's the cure?
--
Best Wishes,
Ashutosh Bapat
EntepriseDB Corporation
The Postgres Database Company